Blow molding station for a container stretch blow molding plant and plant comprising one such assembly

ABSTRACT

The invention relates to a station for the stretching/blowing of preforms having an upward-facing open end. The inventive station comprises a bracket that supports a blow mould, a stretch rod and means for controlling the movements of the stretch rod. The aforementioned control means comprise: (i) an actuator, and (ii) a roller and a speed control cam, said roller coming into contact with the speed control cam as the stretch rod enters the blow mould, thereby controlling the speed with which the stretch rod enters the blow mould. The invention is characterised in that the speed control cam is disposed below the base of the blow mould.

TECHNICAL FIELD

The present invention relates in general terms to the manufacture ofcontainers made of a thermoplastic, such as PET or PEN by a stretch-blowmolding process, from a parison.

The invention relates particularly to stretch-blow molding machines ofthe rotary type, that is, comprising several blow molding stationsmounted around the perimeter of a carousel which is rotated continuouslyabout its axis. Each blow molding station comprises among other things ablowing mold, a blowing device and a stretch device.

The following definitions are given for reasons of clarity only.

These definitions refer to the terminology commonly used in the tradeson which the present invention has some bearing.

“PET” means poly(ethylene terephthalate), that is to say a polyesterproduced for example by polycondensation from terephthalic acid andethylene glycol.

“PEN” means poly(ethylene naphthalate). This is also a polyester.

“Parison” means a preform or intermediate container.

A preform is generally a roughly tubular object closed at one axial end,its opening being in the final shape of the neck of the final hollowbody, such as a bottle.

“Blow molding” means a process in which the parison is placed in afinishing mold containing the impression of the container to beobtained, a blowing nozzle being connected to the opening (the neck) ofthis parison, and a high-pressure blowing fluid being used to push theparison material against the mold walls. The finishing mold may be ahinged mold. The blowing fluid is usually air.

“Stretch-blow molding” means a process in which a stretch rod (alsoknown as a stick) stretches the preform down into the blowing mold bypushing against the bottom wall of the preform. Such a process is usedin so-called simple blow molding machines. Such a process is usedparticularly for blowing previously injection-molded preforms, wherestretching (or elongation) is performed before or during the blowing ofthe preform. Where the stretching occurs before the blowing, preblowingis performed to ensure in particular that the material does not stick tothe stretch rod. Before stretch-blow molding, the thermoplastic preformsare heated in a conditioning oven to raise them to a temperature abovethe glass transition temperature of the thermoplastic material.

“Stretch-blow molding” is also used here to refer to a process in whicha stretch rod is used to stretch an intermediate container. Such aprocess is used in so-called double blow molding machines.

BACKGROUND OF THE INVENTION

As set out for example in document FR 2 764 544 by the Applicant, thestretch rod is conventionally introduced into the opening (the neck) ofthe parison which is to be stretched and blown. This stretch rod slidesthrough a member known as a nozzle. The rod slides axially along thelongitudinal axis of the nozzle and an annular space is left unoccupiedaround this rod for the blowing fluid to pass through.

Stretching a PET parison and preblowing it at medium pressure (e.g. 7bar) lead to an axial elongation speed of around 0.8 to 1.2 m/s. Theradial stretching produced by high-pressure blowing (e.g. 40 bar)presses the material against the mold walls which are cooled, forexample by an internal chilled water circuit.

It is very important for the quality of the blow-molded product tocontrol the speed of axial elongation. It is also important tosynchronize the movement of the stretch rod with the start of blowing.The kinematics of the stretch rods must therefore be controlled, butcontrol is difficult, especially in modern stretch-blow molding machineswhich run at very high speeds.

The stretch speed is conventionally controlled by a roller and camdevice mounted at the top of the machine. This device is so conventionalthat it is often not even depicted (see for example the Applicant'sdocument FR 2 863 929).

This roller and cam device is designed to synchronize the axial positionof the stretch rod with the angular position of the blow molding stationaround the axis of rotation of the carousel.

The appended FIG. 1, which is taken from the Applicant's document FR 2814 392, illustrates a conventional configuration of this roller and camcontrol.

The prior-art machine illustrated in FIG. 1 is rotary: it comprisesseveral stretch-blow molding stations 12 mounted on a carousel 14. Thecarousel 14 is rotated continuously about its axis A1. Each stretch-blowmolding station 12 comprises a blowing mold 16, a blowing nozzle 18, astretch rod 20, and control means 22 for controlling the movements ofthe stretch rod 20. The rods 20 are attached at their top end to aslider 24 which can slide vertically on a rail (not shown) mounted onthe carousel 14. The blow molding station comprises a pneumatic thrustcylinder controlled on a fully-on or fully-off basis and acting on theslider 24 to push it axially down. The stretching speed is controlled bya control cam that forms a helix about the axis A1 of the carousel 14.The slider 24 comprises a roller 38 which, under the action of thethrust cylinder 34, pushes against said cam. When the rod 20 rises, thecontrol chamber of the thrust cylinder 34 is vented to atmosphere. Atthis point, because of the presence of the seal 40, only the lower endof the rod 20 is exposed to the blow molding pressure. The rod 20 istherefore now subjected to an upward axial force equal to the blowmolding pressure multiplied by the transverse area of the rod insection. Depending on the individual case, this force may be of around50 to 150 daN, which is enough to compensate for the weight of the rod20 and of its control mechanism, and thus move the rod 20 back to itsretracted position. It is preferable to provide a safety cam 42 similarto the control cam but designed to force the rod 20 back to itsretracted position if the roller 38 touches it. The safety cam 42ensures that the rod 20 is disengaged from the mold 16 when it is wishedto eject the container at the end of the molding operation even if,owing for example to the preform 10 bursting during molding, thepressurized air escapes from the mold.

Document FR 2 863 928, also in the Applicant's name, sets out anotherform of stretch rod movement control, using a roller and control cammechanism. Two fixed circular and superposed control cams each define ontheir inner face a rolling surface for two pusher rollers. These rollingsurfaces are provided with humps. The pusher is made to rotate as therollers roll over these humps. A compass mechanism converts therotational movement of the pusher into a vertical linear reciprocatingmovement of the stretch rod.

The stretch rod movement control means described in document FR 2 814392 or FR 2 863 928 are perfectly satisfactory in terms of the operationof the stretch-blow molding process.

However, the need to significantly reduce the height of stretch-blowmolding machines has become clear. The arrangements described indocuments FR 2 814 392 and FR 2 863 928 for the control cam and thecontrol thrust cylinders make the machine very tall.

Furthermore, the presence of control cams near the mouths of the bottlesas they come out of the molds can lead to accidental contaminationbecause the cams are necessarily lubricated.

It is one of the objects of the invention to solve these problems.

SUMMARY OF THE INVENTION

To these ends, the invention relates, in a first aspect, to a stationfor the stretch-blow molding of preforms with their open end uppermost,comprising a console supporting a blowing mold; the station alsocomprising a stretch rod and control means for controlling the movementsof the stretch rod, these control means comprising on the one hand anactuator, and on the other hand a roller and a speed control cam, saidroller pressing against said speed control cam as the stretch rod entersthe blowing mold, thus controlling the speed of entry of this stretchrod into the blowing mold, the speed control cam being locatedunderneath the base of the blowing mold.

The mold may for example be a hinged mold.

The blow molding station comprises a blowing nozzle.

In accordance with various embodiments, the stretch-blow molding stationaccording to the invention has the following features, optionally incombination:

-   -   the actuator is a pneumatic or hydraulic thrust cylinder;    -   the station comprises means for the removable assembly of the        stretch rod to the control means for controlling the movements        of this stretch rod.

In order to make it possible quickly to change the standardized stretchrod, the removable assembly means comprise a removable casing in whichone end of the stretch rod is fixed, the other end of the stretch rodbeing intended to be inserted into a parison present inside the mold.

The roller is advantageously mounted at the very bottom of anapproximately vertically sliding pole, this pole being connected, at itsopposite or top end, to an approximately transverse bar mechanicallyconnecting the stretch rod to the rod of the thrust cylinder.

In an advantageous embodiment, the casing is fixed to the transversebar.

In order to coordinate the downward movement of the stretch rod withthat of the thrust cylinder rod, the upper end of the rod of the thrustcylinder is fixed to the transverse bar.

In order to reduce the total height of the stretch-blow molding station,the roller presses against the top edge of the cam as the stretch roddescends into the parison present inside the mold.

In order to reduce the total volume of the stretch-blow molding station,the thin pole, the stretch rod and the rod of the thrust cylinder aremutually parallel.

In order to coordinate the downward movement of the stretch rod into theparison present inside the mold with the rolling of the roller along thecam controlling this descent, the actuator is controlled in such a waythat the thin pole exerts a vertical downward force on the cam when theroller is rolling along the cam.

In order that the rod returns to its initial position before the stretchblow molding operation, the actuator is able to raise the stretch rodonce the rod has finished stretching the parison present inside the moldand/or once the roller is no longer pressing on the cam which controlsthe speed of descent of the rod.

In a second aspect, the invention relates to a carousel-typestretch-blow molding machine comprising:

-   -   a revolving frame rotating about an axis of rotation;    -   several stretch-blow molding stations supported by the revolving        frame;    -   a revolving fluid-supply column coaxial with the axis of        rotation of the revolving frame; and    -   at least one revolving fluid connector located on said column        and connected to fixed sources of fluids,        this machine comprising at least one stretch-blow molding        station as set out above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood more clearly from a reading of thefollowing detailed description of certain preferred embodimentspresented purely by way of illustration, no limitation being implied.

This description will refer to the appended drawings, in which:

FIG. 1 is a view taken from the Applicant's document FR 2 814 392;

FIG. 2 is a perspective view of a stretch-blow molding station in oneembodiment of the invention, certain component parts of the stationbeing shown in an actuated extended position not fixed to the rest ofthe stretch-blow molding station for the sake of clarity and legibilityof the figure;

FIGS. 3 and 4 are views of the stretch-blow molding station shown inFIG. 2, seen from other angles;

FIG. 5 is a perspective view of a stretch-blow molding station in thepreferred embodiment of the invention, with the various component partsof the station connected to each other and the station being in a restposition;

FIG. 6 is a perspective view of a stretch-blow molding station accordingto the invention, the station being in an intermediate position betweenthe rest position shown in FIG. 5 and the final position where thestretch rod is fully extended into the mold; and

FIG. 7 is a perspective view of a stretch-blow molding station accordingto the invention, the station being in the final position where thestretch rod is fully extended into the mold.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

The reader should refer initially to FIGS. 2 and 3.

These FIGS. 2 and 3 show a stretch-blow molding station 100 of a rotarystretch-blow molding machine.

The term “rotary stretch-blow molding machine” is used here to denotecarousel type machines comprising:

-   -   a revolving frame rotating about an axis of rotation;    -   several stretch-blow molding stations supported by the revolving        frame;    -   a revolving fluid supply column coaxial with the axis of        rotation of the revolving frame; and    -   at least one revolving fluid connector mounted on said column        and connected to fixed sources of fluids.

Revolving stretch-blow molding machines may have several tens ofstretch-blow molding stations distributed around a central fluid supplycolumn.

This invention also relates to such a stretch-blow molding machine ofthe carousel type comprising a stretch-blow molding station according tothe invention and as illustrated in FIGS. 2-7.

The preforms are blown with their open end toward the top of FIG. 2, sothat the blowing nozzle and the stretch rod are above the mouth of themold. It is from this arrangement that the notions of verticality, top,bottom, upper and lower which will be used in this text are derived.

The rotating machine is provided with cams 200 to control the movementof the stretch rod 2700. One of these cams 200 is shown in FIG. 2, thiscam 200 being fixed at both ends to the fixed frame of the rotatingmachine, the frame not being shown in order to simplify the drawing.

The cam 200 is mounted on the fixed frame by a lower bracket 300 and anupper bracket 400, these brackets 300, 400 being screwed to the cam 200and to the fixed frame of the machine. To this end, each bracket 300,400 is in the form of an I section, one of its flanges being against thecam 200 and a lower transverse wall being against the fixed frame of themachine.

Each station 100 supports a hinged mold. “Hinged mold” refers forexample to the molding devices described in patents FR 2 646 802, FR 2653 058, FR 2 737 436 and FR 2 843 714, all in the name of theApplicant.

In the embodiment illustrated, the mold comprises two shell holders 500,600 hinged about an axis 700, and a base 800, this base 800 beingmovable along an axis essentially parallel to the axis 700.

The two shell holders 500, 600 have mating faces or bearing facesdefined by meeting bars 900, 1000. These meeting bars 900, 1000 define aparting line for the mold.

An internal molding part or shell 1100, 1200 is fitted to each shellholder 500, 600. The fitting is advantageously detachable so that theshell holders 500, 600 forming the outer structure of the mold can befitted with different shells 1100, 1200 machined to suit the shape ofthe container to be produced.

During stretch-blow molding, the material of the parison presses againstthe inside wall of the shells 1100, 1200.

On each shell holder 500, 600, a projecting external lug 1300 givesrotary support to one end of an actuating link 1400. The other two endsof the two actuating links 1400 come together and rotate freely on ashaft that can be moved linearly toward the mold opening/closing axis700.

The mold is provided with locking means. The locking means comprise, onone shell holder, pins 1500 and a locking shaft 1600. The locking meansinclude rings 1700 on the other shell holder 500.

The locking means prevent the mold from opening or gaping when very highpressure blowing fluid is introduced.

On the rotating machine, mold opening/closure is effected by therotation of follower rollers 1800 acted upon by a first set of cams (notshown).

Similarly on the rotating machine, mold locking/unlocking is effected bythe rotation of follower rollers 1900 acted upon by a second set of cams(not shown).

In the embodiment shown in FIG. 2, the mold base 800 is movable axially,essentially parallel to the mold opening/closing axis 700. This axialmovement of the mold bases 800 is caused by the rotation of followerrollers 2000 acted upon by a third set of cams (not shown).

It should be noted that the stretch cams 200 are positioned at about thesame height as many other cams: those of the mold opening/closingrollers 1800; those of the mold locking/unlocking rollers 1900; andthose of the mold base axial movement rollers 2000.

Within the thickness of the shells 500, 600 there are cooling circuitsconsisting of channels and/or cavities through which a coolant such aswater flows. Fluid connection ends 2100-2500 for each shell 1100, 1200and for the mold base 800 can be seen in FIG. 2. These ends 2100-2500are connected to the rotating central fluid supply column via hoses (notshown in the figures for reasons of clarity only).

A blowing nozzle 2600 and a stretch rod 2700 are mounted as in the priorart axially on the stretch-blow molding station 100 and run through abody 2800 containing internal passage ways for preblowing, blowing anddegassing fluid.

This body 2800 is of rectangular cross section and its overall shape isroughly cubical.

At the front of this body 2800, a block 2900 contains four housings forelectrically operated valves. This block 2900 is mounted detachably onthe body 2800 by means of screws or the like.

In front of this block 2900, a casing 3000 houses the controls of theelectrically operated valves.

A plate or block 3100 containing internal air channels is mounted on therear face of the body 2800. This plate or block 3100 is mountedremovably on the body 2800, by means of screws or the like. A silencerof the type known per se and not shown in the figures is mounted on theplate or block 3100.

The heads of the screws mounting the casing 3000 on the block 2900 are,like the heads of the screws mounting the block 2900 on the body 2800,all directed toward the front of the station 100. This arrangementfacilitates maintenance assembly and disassembly.

The blowing nozzle 2600 forms the lower part of an assembly that behaveslike a piston. This piston belongs to a ram whose body 2800 acts as thecylinder.

Control means move the blowing nozzle 2600 down until there isleak-tight contact between this nozzle 2600 and the top of the mold. Thecontrol means comprise a fork 3200 that engages with an annular groove3300 on the outside of a tubular part 3400 connected to the upper partof the blowing nozzle 2600.

A transverse cover 3500 is mounted on the body 2800. In theend-of-travel position, an annular damping seal 3600 is pressed againstthis cover 3500.

The fluid power connections (not shown in the figures) are provided onthe rear face of the block 3100.

The perforated interface block 3100 receives at 3700 the fluid powerconnections, advantageously by quick connection.

For disassembly during maintenance work, there is no need to disconnectthe fluids because the interface block 3100 stays on the machine.

During re-assembly, locating pins (not shown) ensure correct positioningof the body 2800 on the interface block 3100: no re-adjustment isrequired.

The fork 3200 is part of a guided unit connected to the rear plate 3100.This guided unit is operated by a cam (not shown in the figures but ofthe type known per se) on a roller 3800. The movement is transmittedfrom the moving unit to the nozzle 2600 by the fork 3200.

The nozzle 2600 is in the down position at rest. The counterforceapplied to keep the control roller 3800 on the cam may be provided intwo different ways:

-   -   a mechanical spring;    -   a pneumatic spring integrated in the form of a piston connected        to and concentric with the nozzle, moving translationally in a        chamber, the upper part of which is under pressure. By adjusting        the pressure, the value of the force can be adjusted. The lower        chamber can thus be used as a means of raising the nozzle.

In another embodiment, the control of the translational movement of thenozzle is provided pneumatically. The nozzle is connected to aconcentric piston moving translationally in a chamber whose upper andlower parts are connected to a pneumatic directional control valve.

The positioning of the nozzle 2600 will now be described.

The down position of the nozzle 2600 is realized by the damped contactof the seal 3600 on the cover 3500. This configuration offers at leasttwo advantages:

-   -   adjusting the down position of the nozzle 2600 does not affect        the position of the assembly made up of the groove 3300/fork        3200/guided unit/roller 3800; the relative position of the cam        with respect to the roller 3800 has not been modified in the        event of modification of the down position of the nozzle 2600;        and    -   the fitting attached to the nozzle 2600, and comprising the seal        for blowing the hollow bodies, does not have to be adjustable on        the nozzle 2600; replacing this seal is a quicker, simpler        operation.

The fitting of the stretch rod and the control of its movement will nowbe described more specifically.

An actuator, advantageously a thrust cylinder 3900, preferably pneumaticor hydraulic, is mounted on the console 4000 of the station 100, thisconsole 4000 itself being fixed, for example by screws 4100, to therevolving frame of the machine. The console 4000 carries the hydraulicor pneumatic directional control valves on it, such as the supplydirectional control valve of the thrust cylinder 3900, on its rear face.

The rod 4300 of the thrust cylinder 3900 extends roughly parallel to themold opening/closing axis 700 and to the stretch rod 2700.

A casing 4400 fixes the stretch rod 2700 to a slider or transverse bar4500 of the thin pole 4600, this transverse bar 4500 itself beingconnected to the rod 4300 of the thrust cylinder 3900.

The stretch-blow molding station 100 therefore comprises means for theremovable connection of the stretch rod 2700 to the means of control ofthe movements of this rod 2700, said removable connection meanscomprising the removable casing 4400 in which is fixed one end of thestretch rod 2700, while the other end of the stretch rod 2700 isdesigned to be inserted into the parison present in the mold during theblowing operation.

The stretch rod 2700 is therefore connected removably and adjustably viathe casing 4400 to the transverse bar 4500, to which the upper end ofthe rod 4300 of the thrust cylinder 3900 is also connected.Consequently, therefore, the stretch rod 2700 is connected removably andadjustably to the rod 4300 of the thrust cylinder 3900 via thetransverse bar 4500.

The thin pole 4600, the stretch rod 2700 and the rod 4300 of the thrustcylinder 3900 are advantageously mutually parallel.

Although in FIGS. 2-4 the stretch rod 2700 and the rod 4300 of thethrust cylinder 3900 are shown passing through and projecting from thetransverse bar 4500, it must be understood that they are shown this waypurely for reasons of clarity and intelligibility, and it must berealized that, in the preferred embodiment, the upper ends of thestretch rod 2700 and of the rod 4300 of the thrust cylinder 3900 areconnected to the transverse bar 4500 and preferably do not project fromor pass through it when the stretch-blow molding station 100 accordingto the invention is in operation.

FIGS. 5-7 show more precisely three successive steps of the stretchingby the stretch rod 2700 inside the mold with the various component partsof the station 100 according to the invention in their exact positionsat the moment of this stretch-blow molding operation.

The use of such a casing 4400 provides many advantages. A change to themanufacture of the container may necessitate the use of a preform whoselength and/or inside diameter may differ from those of the previous run.It may also be necessary to use a stretch rod 2700 whose end whichpushes the base of the preform is differently shaped to the preform usedin the previous production run. Rotating machines often comprise dozensof molds. The use of a casing 4400 allows a quick change of stretch rods2700, because in these cases all that has to be done is to replace thecasing 4400 in order to modify the characteristics of the stretch rod2700, such as its length.

The slider or transverse bar 4500 is connected to the thin pole 4600,which in turn slides vertically relative to the console 4000, with theextreme bottom end of this pole 4600 carrying a roller 4700. This roller4700 presses against the cam 200 when the stretch rod descends into theparison to be blown such as a preform. The cam 200 defines a rollingtrack for the rollers 4700 of the stations 100, the shape of this trackbeing determined by among other things the nominal speeds of descent ofthe stretch rod 2700, for example 1700 mm per second.

In other words, the roller 4700 is mounted on the bottom end of theroughly vertically sliding thin pole 4600, this pole 4600 beingconnected, at its opposite or top end, to the roughly transverse bar4500 which mechanically connects the stretch rod 2700 to the rod 4300 ofthe thrust cylinder 3900.

The thrust cylinder actuator 3900 works permanently in tension, the rod4300 of the thrust cylinder 3900 pointing toward the top of the station100.

In other words, the thrust cylinder actuator 3900 is controlled in sucha way that the thin pole 4600 applies a vertical downward force on thecam 200 as the roller 4700 rolls along the cam 200.

In the position shown in FIG. 2, the stretch rod 2700 is in its lowestposition, corresponding to it pressing on the bottom wall of acontainer, at the end of the blowing operation.

However, it should be pointed out that, for reasons of intelligibilityand clarity, FIGS. 2-4 show the blow molding station according to theinvention with the mold open, the stretch rod 2700 in the fully extendedposition, and the roller 4700 on the thin pole 4600 in the bottomposition. It must nevertheless be understood that when the rod 2700 isfully extended into the mold in the preferred embodiment of theinvention, the mold is closed (so that the interior of the mold cannotbe seen) and the roller 4700 on the thin pole 4600 is bearing on theupper edge of the control cam 200 which determines the speed of descentof the stretch rod 2700.

A cam (not shown in the figures but of a type known per se) mounted atthe very top of the stretch rod 2700 forms an upper end-of-travel stopfor the slider 4500.

FIG. 5 shows a perspective view of a stretch-blow molding station 100 inthe preferred embodiment of the invention in a rest position, that is tosay a position immediately preceding blowing and stretching of thepreform and where the stretch rod 2700 is in its highest position. Atthis moment the roller 4700 of the thin pole 4600 presses against theupper edge of the cam 200.

The downward movement of the stretch rod 2700 is controlled by thedownward rolling movement of the roller 4700 on the cam 200.

Specifically, the roller 4700 presses against the upper edge or profileof the speed control cam 200 as the stretch rod 2700 enters the blowingmold, thus controlling the speed of entry of the stretch rod 2700 intothe parison which is present inside the blowing mold.

The thrust cylinder 3900 then works under constant thrust in order to beable to push the roller 4700 of the thin pole 4600 against the top edgeof the cam 200. The roller 4700 thus bears against the top edge of thecam 200 during the downward movement of the stretch rod 2700 into themold.

Advantageously, in order to return the stretch rod 2700 to its initialposition before the stretch blow molding operation, the actuator 3900 isable to raise the stretch rod 2700 once the rod 2700 has finishedstretching the parison inside the mold and/or once the roller 4700 is nolonger pressing against the cam 200 which controls the speed of descentof the rod 2700.

Alternatively, return means may be provided in the form of a springcapable of raising the thin pole 4600 once the roller 4700 is no longerpressing against the cam 200.

As an alternative, it is also possible to have the roller 4700 pressagainst the bottom edge or profile of the cam 200 which controls thespeed of descent of the stretch rod 2700.

In this case, the actuator 3900 is able to exert an upward force on thethin pole 4600 to press the roller 4700 against the bottom profile ofthe cam 200.

FIG. 6 is a perspective view of the blow molding station in anintermediate position, i.e. when the stretch rod 2700 is partly extendedand has not reached the base of the mold, as is the case in theperspective view seen in FIG. 7.

To summarize, the invention therefore relates to a station for thestretch-blow molding of preforms with their open end uppermost,comprising a console 4000 supporting a blowing mold; the station 100also comprising a stretch rod 2700 and control means for controlling themovements of the stretch rod 2700, these control means comprising on theone hand an actuator 3900, and on the other hand a roller 4700 and aspeed control cam 200, the roller 4700 pressing against the speedcontrol cam 200 as the stretch rod 2700 enters the blowing mold, thuscontrolling the speed of entry of this stretch rod 2700 into the blowingmold; the speed control cam 200 being located underneath the base 800 ofthe blowing mold.

The invention has numerous advantages.

The height of the stretch-blow molding machine can be reduced, comparedwith machines of the same capacity, by approximately one meter. Thecladding structure and the cladding are reduced by the same amount.

The upper frame of the machine is made lighter.

Assembling and disassembling the cam 200 is simplified because it isdone on the bottom of the machine.

Lubricating the stretch cam 200 is done at the bottom of the machine,away from the mouths of the containers, and beneath the molds, so thereis no risk of the molds being contaminated. This is a very considerableadvantage when the blow molding machine is producing drinks bottles.

Unlike conventional assemblies, it has no support for a stretch rodadded to the top of a mold-supporting console. The console 4000 supportsboth a mold-supporting unit and the movement control members of thestretch rod.

The invention has been described in relation to the situation in whichthe blow molding station has a mold with only one cavity. It can also beused in the case of a two-cavity blow molding station comprising twostretch rods.

The invention claimed is:
 1. A station for the stretch-blow molding ofpreforms with their open end uppermost, comprising a console supportinga blowing mold; the station also comprising a stretch rod and controlmeans for controlling the movements of the stretch rod, these controlmeans comprising on the one hand an actuator, and on the other hand aroller and a speed control cam, said roller pressing against said speedcontrol cam as the stretch rod enters the blowing mold, thus controllingthe speed of entry of this stretch rod into the blowing mold; whichstation wherein the speed control cam is located underneath the base ofthe blowing mold.
 2. The stretch-blow molding station as claimed inclaim 1, wherein the actuator is a pneumatic thrust cylinder.
 3. Thestretch-blow molding station as claimed in claim 1, wherein the actuatoris a hydraulic thrust cylinder.
 4. The stretch-blow molding station asclaimed in claim 1, wherein it comprises means for the removableassembly of the stretch rod to the control means for controlling themovements of this stretch rod.
 5. The stretch-blow molding station asclaimed in claim 4, wherein said removable assembly means comprise aremovable casing in which one end of the stretch rod is fixed, the otherend of the stretch rod being intended to be inserted into a parisonpresent inside the mold.
 6. The stretch-blow molding station as claimedin claim 2, wherein the roller is mounted at the very bottom of anapproximately vertically sliding pole, this pole being connected, at itsopposite or top end, to an approximately transverse bar mechanicallyconnecting the stretch rod to the rod of the thrust cylinder.
 7. Thestretch-blow molding station as claimed in claim 6, wherein the casingis fixed to said transverse bar.
 8. The stretch-blow molding station asclaimed in claim 6, wherein the upper end of the rod of the thrustcylinder is fixed to the transverse bar.
 9. The stretch-blow moldingstation as claimed in claim 1, wherein the roller presses against thetop edge of the cam as the stretch rod descends into the parison presentinside the mold.
 10. The stretch-blow molding station as claimed inclaim 6, wherein the thin pole, the stretch rod and the rod of thethrust cylinder are mutually parallel.
 11. The stretch-blow moldingstation as claimed in claim 6, wherein the actuator is controlled insuch a way that the thin pole exerts a vertical downward force on thecam when the roller is rolling along the cam.
 12. The stretch-blowmolding station as claimed in claim 1, wherein the actuator is able toraise the stretch rod once the rod has finished stretching the parisonpresent inside the mold.
 13. The stretch-blow molding station as claimedin claim 1, wherein the actuator is able to raise the stretch rod oncethe roller is no longer pressing on the cam which controls the speed ofdescent of the rod.
 14. A carousel-type stretch-blow molding machinecomprising: a revolving frame rotating about an axis of rotation;several stretch-blow molding stations supported by the revolving frame;a revolving fluid-supply column coaxial with the axis of rotation of therevolving frame; and at least one revolving fluid connector located onsaid column and connected to fixed sources of fluids, wherein saidmachine comprises at least one stretch-blow molding station as claimedin claim 1.